Apparatus for flash preheating of pulverulent material



Sept. 27, 1955 L. PETERSEN 2,719,034

APPARATUS FOR FLASH PREHEATING OF PULVERULENT MATERIAL Filed June 10,1954 i 3o k 7 Tfl 26 FIG. I p 27 28 50 g; NVENTOR. BY @SQ VI ATTORNEYSUnited States Patent APPARATUS FOR FLASH PREHEATING OF PULVERULENTMATERIAL Louis Petersen, Rye, N. Y., assignor to F. L. Smidth & Co., NewYork, N. Y., a corporation of New Jersey Application June 10, 1954,Serial No. 435,722

2 Claims. 01. 263-33) This invention relates to the thermal treatment ofgranular and pulverulent material and is concerned particularly with anovel installation for such treatment, which includes a rotary kiln andmeans for carrying out heat exchange between the exhaust gases from thekiln and the material to be supplied to the kiln for burning therein. Inthe installation of the invention, the heat exchange is carried out bycausing the materials to be entrained and carried along in suspension inthe exhaust gas stream, after which the materials thus preheated areseparated from the gases and introduced into the kiln.

In plants of the type described, and especially those employed in theburning of cement raw materials according to the dry process, the use ofpreheaters makes it possible to carry on so large a part of the heatexchange between the kiln gases and the materials to be burnt, that thekiln itself, may be of substantially shorter length than would otherwisebe the case. The reduction in kiln length has resulted in the kiln gasesleaving the kiln at a higher temperature and, in the usual installation,in which the upper end of the kiln extends into a smoke chamberconnected to the preheater system, the higher temperature of the exhaustgases has subjected the smoke chamber and the sealing means between thekiln and the chamber to severer thermal stresses. Also, leakage ofoutside air into the gas stream at the seal between the kiln and thesmoke chamber in such installation results in greater heat loss, becausethe drop in the temperature of gases occurs before they have given upany heat to the raw material.

The present invention is directed to the provision of a plant forthermal treatment of granular and pulverulent materials, which includesa preheating system but avoids the difficulties encountered in priorinstallations, in which short kilns and preheaters are employed. The newplant includes no smoke chamber and it is provided, instead,

with a connecting section, by which hot gases from the kiln may be leddirectly into a riser pipe forming part of the preheating means. In thenew installation, the connection between the kiln and the riser pipeisof substantially less diameter than the kiln and sealing means areprovided to prevent atmospheric air from traveling along the connectingsection and entering the gas stream issuing from the kiln. Since theannular leakage path in the new plant is of substantially less diameterthan the outer diameter of the kiln, the sealing of the path is easierthan in prior installations including a smoke chamber and there is lessheat loss as a result of leakage.

For a better understanding of the invention, reference may be made tothe accompanying drawings, in which Fig. l is a diagrammatic view,partly in elevation and partly in vertical section, of one form ofapparatus embodying the invention;

Fig. 2 is a fragmentary vertical sectional view on an enlarged scale ofpart of the apparatus shown in Fig. 1;

Fig. 3 is a view similar to Fig. 2, of a modified construction; and

Fig. 4 is a fragmentary vertical sectional view on an enlarged scale ofthe sealing means employed in the installation shown in Fig. 3.

The installation illustrated in Fig. 1, includes a rotary kiln 10, whichis of conventional construction except vfor being provided at its upperend with a flange 11 extending radially inward. The cylindrical shell ofthe kiln and the flange are provided with the usual lining 12 and theflange has a central opening 13 for introduction of the material to beburned and the escape of exhaust gases. Theburned gases leaving the kilnenter a preheating system, which includes a generally vertical riserpipe 14 having an elbow 14a at its lower end, the elbow and pipe havinga lining 15. A connecting section 16 of heat resistant metal and ofgenerally conical form is mounted by means of its small end on the openend i of elbow 14a and the connecting section extends into the kilnthrough the opening 13 in flange 11, so that the large end of thesection is wholly within the kiln. The leakage of gases along theconnecting section through opening 13 into the kiln is prevented bysealing I 18 are bolted together and ring 17, which projects outwardlybeyond ring 18, carries a cylindrical sleeve 19. A cylindrical section20 is secured, as by welding, to the outer face of flange 11 on the kilnto encircle the sleeve 19 and section 20 has a circumferential flange200, against which a sealing ring 21 is resiliently held by bolts 22encircled by springs 23. The openings in ring 21, through which thebolts pass, are somewhat enlarged, so that ring 21 can adjust itself onflange 20a, as may be required. Ring 21 extends inwardly from section 20and is provided at its inner end with a flange 21a, which bears againstor is slightly separated from the outer surfaceof sleeve 19. With theconstruction described, the leakage of air along the connecting section16 into the kiln through opening 13 is largely prevented and the sealingring 21 may adjust itself, as the kiln expands and contracts, so that itwill be eflective as a seal in cooperation with sleeve 19. j

The raw material to be burned is contained in a bin 24 having a hopperbottom, from which a duct 25 leads into the riser pipe 14 through anopening in the wall thereof. The lower end of duct 25 may be closed by avalve member 26 mounted on one end of a lever 27 pivotally mounted onthe outside of pipe 14 and urged by a weight 28 to hold the valve membernormally against the lower end of duct 25. The riser pipe 14 continuesupwardly beyond the lower end of duct 25 to enter a cyclone separator 29having an outlet for gases, which is connected by a pipe 30 to theintake of a fan 31. The discharge of the fan is connected by a pipe 32to a dust collector 33 having a gas outlet connected by a duct 34 to astack 35. The dust collector has a hopper bottom with an outlet forsolids, from which a pipe 36 leads. The separator 29 has a hopper bottomwith an outlet for separated solids, which is connected by a pipe 37 toan inlet 14b extending through the wall of elbow 14a of the riser pipe14. A sealing device 38 of conventional construction is mounted in pipe37 to permit the passage of material while preventing the passage ofgases. The pipe 37 may be provided, if desired, with a fitting 39, towhich pipe 36 from the solids outlet of the dust collector may beconnected, so that the recovered dust may be mixed with the separatedsolids and introduced into the elbow 14a. The material thus entering theelbow flows along the inner surface thereof into the Patented Sept. 27,1955,

connecting section 16, from which it is discharged into the upper end ofthe kiln.

With the construction described, it will be apparent that, since theconnecting section 16 decreases in diameter in the direction of gasflow, the 'hot gases leaving the kiln will not'be subject to turbulence.As the gases travel through elbow 14a and enter the riser pipe, rawmaterial is introduced into the gas stream through pipe and some of thematerial is entrained and carried along in suspension in the stream,while the remainder falls into the elbow 14a. In the travel with thegases, the material takes up heat from the gases and the entrainedmaterial is separated from the gases in separator 29 and fedintothelkiln. By feeding the preheated materials so that they flow alongthe inner wall of the elbow 14ainto the kiln, the materials can enterthe kiln without'b'eing picked up thereby to an undesirable extent.

In the modified construction shown in Figs. 3 and 4, the connectingsection between the kiln and the riser pipe is mounted on the kilnrather than on the pipe and appropriate changes in the sealing deviceare made. The kiln 10 is thus formed at its upper end with an integralextension '16 of generally conical form and serving as the connectingsection. The riser pipe 14 has the form of a vertical stack with alateral opening 40 at its lower end and the pipe is provided with alining 41 and is cut away beneath and along the sides of opening 40, sothat a part of the lining 41 defining the bottom and sides of theopening is unsupported. The opening at the end of the conical section 16on the kiln is aligned with the opening '40 and, in order to preventleakage into the stack through opening 40, a sleeve 42 is mounted on theriser pipe around opening 40 and spaced from the end of section 16'. Anangle iron 43 is mounted within the sleeve with one flange extendinginwardly and a fiat ring 44 is mounted within sleeve 42 in spacedrelation to the inward flange of angle iron 43. A flat ring 45 looselyencircling the end of the conical extension 16' enters the space betweenthe flange on angle iron 43 and the ring 44, and a pair of wear rings 46engage opposite faces of ring 45 between the flange and ring 44. Withthe construction described, the leakage of air through opening 40 intothe stack ispreve'nted.

In the installation shown 'in Figs. 3 and 4, the top of stack 14' isconnected by a pipe 47 to a dust collector 48 .having a gas outletconnected by a pipe 49 to a stack (not shown). The raw material is fedby a conventional feeder 50 into the stack through a plurality ofopenings through the top of the stack. The material falling through thegas stream traveling upwardly through the stack is heated by the gasesand collects in a pile 51 at the bottom of the stack. The materialentrained by the gases is separated from the gas stream in the dustcollector 48, which has a hopper bottom. The stack 14 has an inlet 52,to which a pipe 53 containing a conventional seal leads from the bottomof the dust collector 48. The solids from the dust collector are thusdeposited on'the pile 51 and, when the pile has reached the properheight and slope, additional material landing upon the pile aftertraveling down through the stack 14 or through the pipe 53, slides downthe surface of the pile and enters the kiln through the conicalconnectingsection16.

In both forms of the installation illustrated, the use of the connectingsection mounted either on the riser pipe or on the kiln makes itunnecesary to employ the usual smoke chamber, into which the upper endof the kiln projects. As a result, the sealbetween the stationary andmoving parts at the upper end of the kiln is of substantially lessdiameter than informer installations including a smoke chamber and theheat losses from air leakage are substantially reduced.

I claim:

1. An installation for thermal treatment of granular or pulverulentmaterial, which comprises a rotary kiln having an opening at its upperend for introduction of said material to be burned and escape of exhaustgases of combustion, a riser pipe for conducting away the gases from thekiln and havingan open lower end opening for intake of the gases, aconnecting section of generally conical form having its small e'ndsecured to the pipe in alignment with the opening thereof, the sectionextending directly into the upper end of the kiln through the openingthereof, sealing means adjacent the small end of the connecting sectionmounted partly on thepipe and partly on the kiln and preventing passageof air along the outside of'the section into the kiln through theopening thereof, means for introducing material .into the pipe to beheated'by the gases, 'means for separating entrained material from thegases, and means for introducing the separated material through theconnecting section into the upper end of the kiln.

2. An installation for thermal treatment of granular or pulverulentmaterial, which comprises a rotary 'kiln having an opening at its upperend for introduction of said material to be burned and escape of exhaustgases of combustion, a riser pipe for conducting away the gases fromth'e'kiln and having an open lower end opening for intake of the gases,a connecting section of generally conical form having its small endsecured to the pipe in alignment with the opening thereof, the sectionextending directly into the upper end of the kiln through the openingthereof, sealing means adjacent the small end of the connecting sectionmounted partly on the pipe and partly on the kiln and preventing passageof air along the outside of the section into the kiln through theopening thereof, means for introducing material into the pipe tobeheated by the gases, means for separating entrained material from thegases, and means for introducing the separated material into the riserpipe on an inclined inner surface adjacent the lower end opening, thematerial traveling along said surface and through the connecting sectioninto the kiln.

References Cited in the file of this patent UNITED STATES PATENTS1,319,700 Guild Oct. 28, 1919 1,679,337 Moulden et al July 31, 19282,332,724 Johnson Oct. 26,1943 2,590,090 De Vaney Mar. 25, 19522,648,532 Muller et al Aug. 11, 1953 2,663,560 Mulleret a1 'Dec. 22,1-953

